Method of finishing ice trays



July 6, 1954 s. R. FRANCE ETAL 2,633,113

METHOD OF FINISHING ICE TRAYS Filed Jan. 16, 1951 2 Sheets-Sheet 1 CL E'AA/ DOUBLE- GOLD BIA/6E- AA/OD/ZE- COL 0 BIA/6E SEA L WAX INVENTOR. &AA/Lf ;e peA/YCE- A/ [I142 040 JEE/NOL Patented July 6, 1954 METHOD OF FINISHING ICE TRAYS Stanley R. France and Harold J. Reindl, Dayton,

Ohio, assignors to General Motors Corporation,

Detroit, Mich., a corporation of Delaware Application January 16, 1951, Serial No. 206,202

2 Claims.

This invention relates to ice trays and is particularly concerned with chemical treatments for the surfaces of said trays to enhance their appearance and to improve their workability. It is, therefore, the basic object of the invention to provide a method for treating ice tray surfaces to yield an improved appearance thereon and simultaneously to provide a protective coating thereover which prevents the adherence of water or ice to the tray. In carrying out the above object, it is a further object of the invention to chemically brighten the surfaces of aluminum ice trays, anodize said surfaces, dye the anodized surfaces to provide a suitable attractive color thereon, seal the dye within the anodic pores of the surfaces'and finally to provide a protective coating all over the surfaces of the ice tray for maintaining the brightness and color thereof while simultaneously acting as a medium for substantially preventing the adherence of water and Further objects and advantages of the present I invention will be apparent from the followin description, reference being had to, the accompanying drawings, wherein preferred embodiments of the present invention are clearly shown.

In the drawingsz' v Fig. 1 is a flow chart showing the major steps in the process for treating an ice tray.

Fig. 2 is a diagrammatic view of a treating tank wherein the length of each chamber is designed to provide the proper relative period of immersion for an ice tray passing therethrough at a constant rate. j r The process, to be described hereinafter, is used in connection with ice trays and similar articles wherein the tray is preferably made of aluminum or aluminum alloy material, although other metals, which may be anodized and chemically brightened, can be utilized. For this reason, the term aluminum as used hereinafter is to be considered generic, and to include that entire class of metals which are adapted to chemical brightening and color anodizing.

The use of anodized surfaces on aluminum ice trays is admittedly 01d. It,is also known that day ice trays having manual ejectors maybe used to freeze ice cubes and the like wherein after the freezing is accomplished, the cubes may be readily freed from the surfaces of the tray by the manipulation of a handle which moves certain surfaces only of the tray. The coating material reduces the tenacity of adherence of the ice to such an extent that it is an easy matter to remove the cube from the tray which is so treated.

We are also aware that aluminum articles have been color anodized wherein the anodized surface, including a myriad of microscopic, anodic pores, is filled with a dye in solution, which dye, upon drying within the pores, yields a colored appearance to the article.

The present invention is directed, in the main, to an improved process including a plurality of steps, which cooperate, one with another, to provide an article of improved appearance wherein the brightness of the article is heightened, the color is enhanced and the whole article is protected by a wax-like coatin which has the dual purpose of preventin leaching of the color by materials'contained in the tray while simultaneously preventing tight adherence of the ice to the surfaces of the tray. The main steps of the process are shown in connection with the flow chart sufficiently smooth to present a polished, bright surface appearance. This may be obtained rather easily by the leveling action of a chemical brightening bath. Baths of this nature are well known in the art and the particular bath to be used is not critical so IOIlg as the desired result is obtained. In this connection two chemical brightening baths are disclosed in copending applications, Serial Nos. 148,271 and 191,324, both assigned to the assignee here. In general, various combinations of phosphoric and nitric acids, with or without sulphuric acid, together with nitric acidhydrofluoric acid baths, all yield satisfactory results of varying degree. The concentrations, temperature, etc., of these baths for their best operation is well known in the art.

After the surfaces of the aluminum ice trays are brightened by the leveling action of a brightening bath, the tray is next placed in an anodizing tank wherein its surfaces are anodized. In this connection, we prefer to use a 15% sulphuric acid solution wherein the tray is made the anode of a cell and wherein an anodic coating having thickness in the order of .00009 to .0002 inch is believed to be the most desirable range of thickness. Here again, anodizing methods and controls are widely known together with their variations. For example, chromic and phosphoric acid baths are known for this purpose. After anodizing, the tray is placed in a dye solution, such as an aqueous solution of an organic dye of such character as will pass the restrictions set down by the Pure Food and Drug Act. This dye is added to water in the dyeing tank in concentrations and under conditions sufficient to yield the desired color.

We take advantage of the dyeing step to simultaneously seal the pores of the tray by maintaining the dye bath at a temperature of between 175 and 210 F. plus or minus 5. Thus, as dye enters the anodic pores, the pores are sealed off by the action of the hot dye bath whereupon the dye is fairly well occluded within the surface of the aluminum. The tray is then removed from the dye bath and thoroughly rinsed with cold and then hot water and dried either by the evaporation of said water or by the action of a drying oven shown, whereupon the tray is immediately immersed in a wax-like material which is maintained in a fluid condition through heat and/or solvent. The wax-like material may be beeswax, carnauba wax, parafiin or any other high molecular weight wax of the methane series, mixtures thereof, etc., or the coating may be a mixture of waxes and resins, for example, as disclosed in the Geyer and Canter Patent No. 2,l04,l31. Here again, the particular waxy coating used is of little importance so long as it protects the surface, prevents the adherence of ice and is transparent so as to not reduce the attractiveness of the color and the brightness of the metal therebeneath.

The uninterrupted sequence of the steps is of prime importance since at all times until the drying step, the tray surfaces are wet with water or other solution which acts as a protective coating to prevent oxidation of the cleaned and brightened surfaces. The waxing should also be in direct sequence since this too aids in maintaining the color and brightness of the tray and furthermore acts as a protective covering on the surfaces of the ice tray when in use. Wax is an old expedient to prevent water and ice adherence but in the present instance, the wax serves an-- other purpose, namely, it prevents the colored surfaces of the tray from being directly contacted by foodstuffs, such as citric acid juices, which, without the protective wax, tend to leach out the color. This tendency is more pronounced with some dyes than with others but in all cases, the protective wax coating effectively prevents leaching or change in color when the tray is used with any of the usual foodstuffs and fluids encountered in home use.

It will be noted that the process is a continuous one with treating steps being interspersed by washing or rinsing so that reagents are not carried from one treating tank to the next. In all cases, it is desirable to maintain the concentration of reagents in the several tanks at as constant a figure as is possible. In this respect automatic addition devices may be used or the tanks may be replenished at stated intervals b fore the strength is reduced to a point that the efficiency is markedly effected. All rinse tanks are preferably equipped with sprays at the entrance and exits thereof to promote the best possible cleaning elfect and to prevent carryover. In all tanks, it is desirable to agitate the contents to prevent Stratification or settling, although this may be dispensed with in some cases.

The drying step is effected by rinsing in hot water and then carrying the hot clean tray in the atmosphere a suflicient distance to permit evaporation of the water. An alternative is to provide a short drying oven or tunnel (shown at 22) wherein forced hot air is directed against the trays whereby an accelerated drying step is accomplished.

The time of immersion in the various tanks regulates to some extent the results of the process. It is manifest that this time vary widely providing the relative times in each tank are maintained. For this reason a unit of time is measured as the period required to transfer from one tank to another. Thus the cleaning step (tank 24) is set up for 9 time units, followed by a transfer of one unit, a rinse of one unit (tank 25) and a transfer of one unit. The chemical brightening step (tank 28) requires 9 time units followed by two rinses (tanks 3% and 32) of 3 units each separated by the transfers. lhe anodizing step (tank 3d) is set up for thirty-one time units followed by a five and a one unit rinse (tanks 38 and 31) whereupon a 19 unit dyeing step (tank 38) followed by two one unit rinses (tanks 40 and 42) and then the drying and waxing step (in oven 22 and tank at) which consumes about 13 units.

While these relative periods of time in each tank are preferred it is'to be understood that the concentration of reagents regulates, to a large measure, the time required to fully process a tray. In all cases, therefore, great variation from the preferred embodiment is possible, the specific figures set forth being illustrative only of one successful combination.

The only requirement that is of absolute importance is to maintain the uninterrupted sequence of the steps so that articles being processed are never allowed to dry or are they allowed to lose the protective filmof liquid on the surfaces thereof as the tray is being transferred from one tank to another. This is very important to the quality of the product since it produces a much brighter tray than when the-steps are widely separated or are not continuous.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In a method for making waxed and colored aluminum ice trays, the steps comprising: cleaning the surfaces of an aluminum ice tray; brightening the surfaces of the tray by immersion in a chemical brightening solution; anodizing the brightened surfaces; dyeing the anodized surfaces by immersing the tray in a hot solution of a soluble organic dye and simultaneously sealing the dye within the pores of the anodized surfaces; continuously protecting the surfaces of the tray against oxidation by the maintenance of a protective aqueous coating thereover throughout the time required to perform said steps and to transfer the tray from one step to the next subsequent step; drying the tray; immediately coating the dyed surfaces of the tray by immersing the dyed and sealed tray in a hot, fluid wax-like material for providing a wax-like covering all over the surfaces of said tray; and then removing the tray from the wax-like material and cooling the same; all of said steps being sequentially performed without delay therebetween and all of said steps except the waxing step being separated by rinsing steps.

2. In a method formaking Waxed and colored aluminum ice trays, the steps comprising; cleaning the surfaces of the tray in an alkaline solution of a strength sufficiently low to prevent any substantial etching; brightening the cleaned surfaces by immersion in an active acidic brightening bath; anodizing said surfaces in a mineral acid solution for forming minute anodic pores therein; impregnating the pores with a solution of an organic dye, sealing the dye within the pores simultaneously by maintaining the dye solution at a temperature in excess of 170 E; continubeing sequentially performed without delay therebetween and all of said steps except the waxing step being separated by rinsing steps.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,294,717 Carney Sept. 1, 1942 2,363,339 Kraft et a1 Nov. 21, 1944 FOREIGN PATENTS Number Country Date 502,278 Great Britain Mar. 15, 1939 OTHER REFERENCES Pullen: Metal Industry, September 18', 1936, pp. 293-5.

Henley: Light Metals, October 1949, pp. 536-41. 

1. IN A METHOD FOR MAKING WAXED AND COLORED ALUMINUM ICE TRAYS, THE STEPS COMPRISING: CLEAN ING THE SURFACES OF AN ALUMINUM ICE TRAY; BRIGHTENING THE SURFACES OF THE TRAY BY IMMERSION IN A CHEMICAL BRIGHTENING SOLUTION; ANODIZING THE BRIGHTENED SURFACES; DYEING THE ANODIZED SURFACES BY IMMERSING THE TRAY IN A HOT SOLUTION OF A SOLUBLE ORGANIC DYE AND SIMULTANEOUSLY SEALING THE DYE WITHING THE PORES OF THE ANODIZED SURFACES; CONTINUOUSLY PROTECTING THE SURFACES OF THE TRAY AGAINST OXIDATION BY THE MAINTENANCE OF A PROTECTIVE AQUEOUS COATING THEREOVER THROUGHOUT THE TIME REQUIRED TO PERFORM SAID STEPS AND TO TRANSFER THE TRAY FROM ONE STEP TO THE NET SUBSEQUENT STEP; DRYING THE TRAY; IMMEDIATELY COATING THE DYED SURFACES OF THE TRAY BY IMMERSING THE DYED AND SEALED TRAY IN A HOT, FLUID WAX-LIKE MATERIAL FOR PROVIDING A WAX-LIKE COVERING ALL OVER THE SURFACES OF SAID TRAY; AND THEN REMOVING THE TRAY FROM THE WAX-LIKE MATERIAL AND COOLING THE SAME; ALL OF SAID STEPS BEING SEQUENTIALLY PERFORMED WITHOUT DELAY THEREBETWEEN AND ALL OF SAID STEPS EXCEPT THE WAXING STEP BEING SEPARATED BY RINSING STEPS. 